Conventionally, there has been proposed a wireless frequency hopping technique in which a carrier frequency is switched according to a hopping pattern. For example, PTL1 discloses a trigger generation apparatus for providing a measurement start trigger to a measurement apparatus that measures a condition of a communication apparatus for performing communication by a frequency hopping system. The trigger generation apparatus has a communication means for data communication with the communication apparatus and a frequency hopping means for switching a frequency used in the communication means. The trigger generation apparatus outputs a trigger at time of communication of a measurement start position in data (e.g., at communication of a payload header of a data packet). In response to the trigger, the measurement apparatus starts measurement. This makes it easy for the measurement apparatus to be synchronized with the communication apparatus.